This invention relates to valves for fluids and has particular application where the fluids are toxic, radioactive or valuable so that leakage into the environment must be reliably prevented, or where the ingress of ambient atmosphere or other fluid environment must be prevented to avoid reaction or for any other reason.
Known valves of this kind designed to prevent outleakage or inleakage are generally provided with a bellows to seal between the longitudinally movable valve closure member and the stationary body of the valve which carries the valve seat upon which the valve closure member is engaged to close the valve. Such valves are hereinafter referred to as of `the specified kind.` Should the bellows fail, however, such valves would be subject to leakage.
It is an object of the present invention to provide a valve of the specified kind with additional safeguards as a precaution against bellows failure.